Uttarakhand PMT Uttarakhand PMT Solved Paper-2008

  • question_answer
    The nucleus of an atom can he assumed to be spherical. The radius of the nucleus of mass number A is given by\[1.25\times {{10}^{-13}}\times {{A}^{1/3}}cm\]. Radius of atom is one A. If the mass number is 64, then the fraction of the atomic volume that is occupied by the nucleus is

    A)  \[1.0\times {{10}^{-3}}\]

    B)  \[5.0\times {{10}^{-5}}\]

    C)  \[2.5\times {{10}^{-2}}\]

    D)  \[1.25\times {{10}^{-13}}\]

    Correct Answer: D

    Solution :

     Radius of nucleus\[=1.25\times {{10}^{-13}}\times {{A}^{1/3}}cm\] \[=1.25\times {{10}^{-13}}\times {{64}^{1/3}}\] \[=1.25\times {{10}^{-13}}\times 4\,cm\] \[=5\times {{10}^{-13}}cm\] Radius of atom \[=1\overset{o}{\mathop{\text{A}}}\,={{10}^{-8}}cm\] Volume of nucleus/ volume of atom \[=\frac{(4/3)\pi {{(5\times {{10}^{-13}})}^{3}}}{(4/3)\pi {{({{10}^{-8}})}^{3}}}\] \[=\frac{125\times {{10}^{-39}}}{{{10}^{-24}}}\] \[=125\times {{10}^{-15}}\] \[=1.25\times {{10}^{-13}}\]


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